Thoracic aortic aneurysms (local dilatation of the artery which is prone to rupture) and dissections (splitting within the arterial wall prone to rupture, branch occlusion and aneurysmal degeneration) occur at a prevalence rate of 6/100,000 and 3/100,000 respectively and without treatment are associated with a high mortality rate which, in some situations, exceeds 50%.
Endovascular repair of aortic aneurysms, both thoracic and abdominal, is now an accepted and often preferred modality associated with a lesser mortality rate and complications compared to open surgical repair.
A large proportion of thoracic aneurysms and dissections involve the ascending aorta and the aortic arch. In these cases, endovascular repair with standard tubular stent-grafts is impossible because the three great vessels arising from the aortic arch (innominate or brachiocephalic artery, left common carotid artery and left subclavian artery), supplying the brain and the upper body, would be occluded. Occlusion of these arteries beyond several minutes can lead to severe complications and death. The current therapeutic alternative is open surgical repair, which in the case of ascending aorta and aortic arch aneurysms and dissections is extremely hazardous, may require total circulatory arrest (complete cessation of blood flow) and is associated with significant mortality exceeding 15-20%.
When a stent-graft is deployed in the aortic arch, it covers arteries that supply the brain. Therefore, it is important that such a stent-graft will have openings that face the brain supplying arteries (BSAs), and often the repair may require that the stent-graft have side-branches going into the brain-supplying arteries. Such openings and/or side branches may be prepared in advance, before the stent-graft is deployed (See, for instance, WO 02/076346, the disclosure of which is incorporated herein by reference), or in situ, when the stent-graft is already at the aorta. Aligning pre-made openings with the patient's BSAs may be difficult and occluding the brain-supplying arteries for a period long enough to allow in-situ preparation of such openings might cause severe brain damage or even death. Additionally, as the location of the BSAs is different in different individuals, a stent-graft with pre-made openings must be prepared for each patient individually, according to his own measures.
To prevent leakage of blood from between a branch stent graft and a main stent graft, the main stent graft may be made with one or more tubular sleeves extending outward from the fenestration. While this solution is customary for bifurcated abdominal aortic stent grafts at the aortic bifurcation, at other sites with greater anatomic variability, or where the space around the stent graft limits maneuvering, this solution is more complex.
A paper titled “In Situ Stent-Graft Fenestration to Preserve the Left Subclavian Artery” authored by Richard G. McWilliams; Micheal Murphy; David Hartley; Michael M.D. Lawrence-Brown; and Peter L. Harris, describes in-situ fenestration of a stent-graft deployed in the aorta while occluding the subclavian artery. However, occluding the left common carotid or innominate artery for the long time required for in-situ fenestration might cause severe damage to the patient.
The article “Modular branched stent-graft for endovascular repair of aortic arch aneurysm and dissection, by Timothy A. M. Chuter et al., published in J. vasc. Surg. 2003; 38:859-63 describes a bifurcated stent-graft inserted from the right carotid artery and extended from there into the ascending aorta. In this publication, two branches are revascularized by surgical bypass and not by stent-graft branches and no shunt was used.